Eliminating the risk of hepatitis infection from therapeutic clotting fractions and other blood components is a problem of high priority. We will study the application to this problem of a separation process in which dissolved proteins are ultrafiltered through a highly selective membrane which prevents appreciable permeation of the virus. Simultaneously, to permit the use of a second strong separation force, the pH will be held different from that of the virus isoelectric point, and an electrophoretic field will be applied to actively hold the virus away from the membrane. This combination of separation techniques will be termed "electroultrafiltration" (EUF). The process has been used to separate dissolved blood proteins having different isoelectric points, while drastically decreasing the build-up on the membrane of the retained, charged, protein. The focus of the study will be on eliminating hepatitis B risk, since serological markers can be used to accurately charaterize the separations. (The process should also be applicable to the elimination of non-A, non-B hepatitis risk, when serological markers become available.) The study will involve removal of hepatitis B virus from clotting factor concentrates and plasma, and the separation of Factor VIII under conditions which prevent viral contamination. The specific phases of the study are: Removal of added HBsAg from commercial factor VIII concentrates; Separation of factor VIII and albumin from normal plasma; Removal of endogenous hepatitis virus from cryoprecipitate from infectious plasma; Separation of virus-free factor VIII from infectious plasma.